Recently, the effect on the human bodies by the electromagnetic waves generated from the personal computers, TV sets and other electrical appliances is a problem. Especially, the mobile phones radiate high frequency waves between 800 MHz and 1.5 GHz. Although the generating power is weak, it is necessary to shield human head from the electromagnetic waves as they are used close to the human head. And the malfunction and the trouble of the Pacemaker and the hearing aids caused by the electrical appliances are becoming a social problem.
Use of the mobile phones in the automatic control system car and the airplane may cause a big accident by malfunctioning the computer system. Moreover, the high frequency electromagnetic waves are harmful to the cell or the immune system in the human bodies and it is on the issue and the study has begun.
In order not to emit the electromagnetic waves, it is effective to use the electromagnetic waves shield. However, mobile phones need to emit the electromagnetic waves for the radio communication. A device is needed to shield the electromagnetic waves only to the head direction.
For this purpose, the ear covers have been attempted to shield the user side from the mobile phone, and an attempt of shielding the electromagnetic waves to the head direction using the plate on the mobile phone wire antenna was made. But, the former is troublesome to wear, and the structure of the latter did not have the enough shield effect.
Also, electric instrument (especially, read only memory including the memory) were many examples that actuate wrong by external noise each. We cannot find the good handling and cheap material for protecting the external noise. It is serious that the important monitor of the hospital actuates wrong and also the pacemaker for the heart diseases actuates wrong with portable telephone and the others especially, and there was not a cheap effective thing the electromagnetic waves shields for the prevention of this external noise.
As the products to prevent from the harmful electromagnetic waves, there have been a nickel coating polyester, OA apron used a metal texture and the like, the transparent hard plastic VDT (Video Display Terminal) filter and so on. The above OA apron is easily stained and the stain is conspicuous. When the material for the above OA apron is used for the mobile phone cases, the thin material causes the deformation of the shape and so on as the mobile phones often held by hands. It is not convenient to use them.
It is necessary to confirm the location, the function, and the content of the indication and the like on the display, the control part of the switch and the keys on the above electric appliances from out side of the cases. It is necessary to cover the cases with the transparent material. However, when the transparent hard plastic material for the above VDT filter is used for the operating part of the switch and the keys and the like, it harms the control of the electric instruments. Because it is unable to operate the switch and the keyboard from out side of the case.
A special loom is needed to weave the texture with micro order metal fiber. It results the high cost of the texture. Accordingly, when the other large-sized appliances like the washing machine and the dryer are taken up as the appliances to be shield from the electromagnetic waves, the required cost of the electromagnetic waves shield will be high. To solve this problem, it could be thought to weave the mesh roughly to reduce the use of the amount of the metal fiber. But it will cause a deformation of the metal fibers because it moves lengthwise and crosswise. Consequently, 1.5 mm, the size of the meshes, cannot be maintained. It is known by way of experiment that the above mesh size of 1.5 mm has the enough effect on the electromagnetic waves shield.